青藏高原东北隅断层活动及地壳变形模式  

Faults activity and crustal deformation pattern on the northeastern corner of the Tibet Plateau

作　　者：徐炜祥 苏小宁 虞思晗 朱庆 XU WeiXiang;SU XiaoNing;YU SiHan;ZHU Qing(Faculty of Geomatics,Lanzhou Jiaotong University,Lanzhou 730070,China;Faculty of Geosciences and Environmental Engineering,Southwest Jiaotong University,Chengdu 611756,China)

机构地区：[1]兰州交通大学测绘与地理信息学院,兰州730070 [2]西南交通大学地球科学与环境工程学院,成都611756

出　　处：《地球物理学报》2024年第7期2596-2611,共16页Chinese Journal of Geophysics

基　　金：国家自然科学基金(42174003);甘肃省科技计划(22JR5RA315);甘肃省青年人才托举工程(GXH20210611-06);兰州交通大学青年科学基金项目(2021003);兰州市人才创新创业项目(2023-RC-31)联合资助。

摘　　要：精准分析青藏高原东北隅断层活动和地壳变形模式对于理解区域大地震空间分布特征和地震危险性分析具有重要意义.本文在已有GPS速度场的基础上,通过建立由21个GPS连续观测站组成的3条跨断层剖面的加密观测,获得研究区较高空间分辨率的GPS速度场.利用K-中心点和欧拉矢量结合的方法分析GPS速度场的空间聚类特征,发现在陇西块体内部存在显著的差异性变形,进而结合区域已有块体-断层划分模型,给出与最新GPS速度场更为吻合的块体-断层模型.改进模型的最大特点是在陇西块体内部存在一条北北东向的右旋剪切带.利用最新GPS速度场和改进的块体-断层模型,基于负位错理论反演主要块体的运动特征和主要断层的滑动速率,结果显示在改进块体-断层模型中新增的右旋剪切带在分配该地区应变积累特征时扮演着重要的角色,进而计算的六盘山断裂的挤压速率远小于已有的结果,其地震危险性也可能相应地降低.The precise analysis of the activity faults and crustal deformation patterns on the Northeastern corner of the Tibetan Plateau is crucial for understanding regional large earthquakes and seismic hazard analysis.Combined with the pre-existing GPS velocity field,we obtained the GPS velocity field with higher spatial resolution in the study area by establishing encrypted observation of three cross-fault profiles composed of 21 continuous GPS stations.We analyzed the spatial clustering characteristics of GPS velocity field by using the combination of K-means clustering and Euler vector.It is found that there are significant differential deformations inside the Longxi block.Combined with the existing block-fault division model,we proposed an advanced block-fault model which is more consistent with the latest GPS velocity field.The major feature of the advanced model is the presence of a NE-trend right-lateral shear zone within the Longxi block.By utilizing the latest GPS velocity field and the advanced block-fault model,we utilized the back-slip dislocation model to infer the motion characteristics of the main blocks and slip rates of the primary faults.The results show that the right-lateral shear zone in the advanced block-fault model plays an important role in allocating strain accumulation characteristics in the region.Consequently,the calculated contraction rate of the Liupanshan fault is notably lower than previous results,suggesting a corresponding reduction in seismic hazard.

关 键 词：青藏高原东北隅 GPS速度场 欧拉矢量聚类分析 负位错模型 滑动速率 

分 类 号：P228[天文地球—大地测量学与测量工程]